Actuating mechanism for artificial hands



E.' w. HoBBs ACTUATING MECHANISM FOR ARTIFICIAL March l5,vt 1949.

4 Sheets-Sheet l Filed Jap. s1, 194e WML @7h47 March 15, 1949. E. w. HOBBS 2,464,577

ACTUATING MECHANISM FOR ARTIFICIAL HANDS 4 SheetsfSheet 2 Filed Jan. 51,` 1946 341A j? 30 2/9 "f5 19 :E I '1f 15 March l5, 1949. E, W, HOBBS 2,464,577

` AGTUATING MEG'IANISM FOR ARTIFICIAL' HANDS '4 sheets-sheet l5 Filed Jn. 51, 1946 March 15, 1949.

E.. W. HOBBS ACTUATING MECHANISM FOR ARTIFICIAL. HANDS 4 Sheets-Sheet 4 Filed Jan. 51, 1946 Patented Mar. 15, 1949 UNITED S''A'i` ACTUATING MECHANISM FOR ARTIFICIAL HANDS Edward Walter Hobbs, Rickmansworth, England This invention relates to mechanical articial hands for use by persons who have suered amputation. These, as are well known are operated to grasp or to release objects by a iiexion cord, wire or the like actuated by shoulder movement, chest movement or pedal movement of the wearer.

The artificial hands at present available are primitive, enable a narrow range only of objects to be grasped and do not permit of the object being securely held. Thus one form'embodies a pivoted and spring loaded thumb which co-operates with xed fingers, being opened against the action of the spring by the pull of the flexion cord. In another form four fingers are pivoted to close as a unit against a fixed thumb under spring pressure. In yet another the four iingers again pivot as a unit to open and close against a xed thumb, being operated from the flexion cord through a worm drive which acts to lock the ngers in the closed position.

In all these constructions the rst and second iingers only co-operate with the thumb, the third and fourth ngers closing only to the same extent as the first and second fingers and contributing but little towards eiective holding of the grasped article.

The invention provides an artiiicial hand comprising a base member, a plurality of digits pivotally mounted on the base member for opening and closing movement in relation thereto; a common operating member for the digits which operates positively on them to open and close them and is self-locking against reverse operation by the digits, and a compensating linkage connecting the operating member and the digits and serving to impart collective movement to the digits from the operating member, said linkage permit- 1o claims. (c1. -3-12) pedal movement, for the purpose of operating the hand and when a spring is employed to move the digits of the hand in one direction a substantial proportion of this small available power is used 5'up in overcoming the spring. f v.

10 ating member.

fifor an additional manual adjustment of any oi l In the preferred form of hand according to the invention, four fingers and a thumb are ara pin, a cricket ball, an electric light bulb or a r cigarette package.

v' f I do, not however exclude the possibility of employinga rigid thumb and compensated pivotal in conjunction therewith.

Again one or more of the fingers may be mainiingers operating tained rigid if desired. I may lfurtherproyide the digits in relation to the base member bythe other hand. Thus, in the case of a rigid thumb this couldbe made settable into two or more posil, tions by such manual adjustment. Such manual 25"'"adjustment may also be provided, if desired, in

the kcase of the compensated. pivoted digit-s.

In the preferred form of hand according to the invention, each iinger is pivoted to the base memy :ber at the base of the nger and consists of two.

30"parts pivoted together at a ypoint corresponding to wwhile the thumb is pivoted to the base member at Y ting, after any of the digits has been arrested,

themiddle knuckle joint, the compensating linkage being connected to the upper portion of each linger so as to cause pivotal movement thereof about both joints as the iinger opens and closes,

its lower end and has no knuckle joint. I prefer moreover to offset the pivots at the lower ends of the finger to correspond with the anatomical ari rangement of the lower knuckles of a normal 46 hand As hereinafter explained in more detail,

With this-form of hand an object can be grasped much more eectively than with the artificial hands at present available, since any of the digits not arrested by an object to be grasped can continue to closeuntil they either reach a limiting position or themselves make contact with the article.

An important advantage of the hand according to the invention is that it dispenses with the use of springs, thedigits being moved positively both in the opening vand closing directions by the operating member. It will be understood that only a limited amount of power can bedeveloped by the use of the shoulder or chest muscles or by a thisis achievedby placing the pivots of the first and third lingers inalignment and at thesame level above the base member, the pivots for'the ,second and fourth (or little) fingers being respec- 5 tively above and below this level, and being rey 'While I prefer to keep the pivotal axes of 'all 55 the fingers parallel theymay be set slightly askew,

3 should it be desired that .the finger tips should approach or splay apart as the fingers close.

The hand according to the invention is especially suitable for use in conjunction with the articial arm described in U. S. application of Joyce Otterman Serial No. 646,133, filed February 7, 1946, whichserves to convert the pull of the exion cord into rotary movement.

The preferred,` form of operating member, in a hand according to the invention, is a screw and nut mechanism, one member of which (preferably the screw) is adapted to receive rotary driving movement and the otherfoffwhich is fixed to the base member, the compensating linkage being operated by axial movement of the drivereceiving member.

The screw and nut mechanism isan-eiilcient operating member, since the screw 4can bemade of small diameter and will therefore turn` atlow peripheral speed, thus dissipating far less of the input energy in friction' than in the caseof a wormv drive which. necessarily turns at a much higher peripheral speed. The screw and nut mechanism is moreover self-locking against re'- verse operation by Aforces applied to the.' fingers, provided the tangent of thelpitch angle of the thread does not exceed l/s. Furthermore it enables alight or, firm contact pressure to be applied at will by the user,r according to the degree of eiiort exerted, giving firm and. positive locking both in the lightpressure and in theiirm pressure positions. Also, by further operation of the' flexion cord, the `user can, should he` wish, increase or diminish the gripping pressure of the ngers 4after the object has' been grasped.

'One specific form ofrartiiicial hand accordingto thev invention, will `now be described in detail,` by way of. example with reference to the accompanying drawings in which:

Fig...1 isa side elevation of thev hand, partlyA in4 section, showingone ofthe fingers closed,

Fig.' 2 is a. corresponding' part-sectional frontview, showing all the fingers open,

Fig. 31isa section on the line'IIITIIIin Fig. 1,

4 is. a` frontelevaton ofthe skeleton struc' ture constituting .the base of .the hand,

Fig. 5 .is a left .handA side view" of the structure shown in Fig. 4,

Like reference characters designate like parts throughout the figures.

The hand comprises a base, constituted by the skeleton structure shown in Figs. 4 and 5, to

which the thumb Iii and the fingers il, l2, i3

bracing members 2 I, 22. All these parts are made Fig. 6 is. a vertical sectionthrough one of. the

iingers and its associated operatinglink,

Fig'.` '7 is acorresponding side elevation,

Fig. 8 is a top plan viewof the structure shown in. Fig. 4, 'with the screw and .nut .mechanism fitted therein,

Fig. 9 is a detail view showing` the connection between the thumb and the screw and nut mechanism,

Fig. 10 is a perspective view of the thumb, with its covering partlybroken away,

Fig. 11 is a plan viewof the. main` linkof the compensating linkage,

Fig. 12 is a. perspective view of the. hand with the. covering partly. broken away ,and showing Athe hand in apartly closed position,

Fig.. 13, is a detailview of one: of the fingeroperatinglinks,

Fig. 14 is. aperspectiveview of thetwo components. of the inner structure. of one ofthe fingers,

`Fig..15 is an exploded` view showing the various components,l of4 the screw .and-.nut mechanismen-d Figs. 16'-1`9are diagrams 'showing'the positions assumed. by, the, compensating linkage under. dif.- fe'rent operating conditions. v

of light metal alloy strip and they are welded or riveted together. This skeleton structure is, of itself, sufficiently strong to take all loads which Vare likely to be imposed on the hand, but it is reinforced to provide a factor of safety by wrapping it externally with metal gauze 23 (see Fig. 12). After assembly within the skeleton structure of the operating mechanism and the mounting thereon of the thumb and fingers, the skeleton structure is .given an external coating 24 (Fig. 12) of plastic material and is afterwards pressedin a mould to shape the plastic material and to cause the same to penetrate into the interstices of the gauze.

A length of rod 25 (Figs. 4 and 8) carried by the buttress 2l] serves as the pivot for the thumb I 0, while lengths of rod 2li-29 serve as the pivots for, the lower ends of the fingers ll-I4 respectively. These extend between metal blocks 30 fitted to the upper ends of the side members i9 of the skeleton, metal blocks 3l fitted to the upperA ends of the tie rods i3, an-d a metal block 32 uniting the upper ends of the front and rear members I7, i3 of the skeleton.

As will be observed from Figs. 4 and 8 the pivots 26, 28 for the first and .third fingers Il, I3` are coaxial, while the pivot 21 for the second finger l2 lies above and behind this common axis, while the pivot 23 for. the fourth fin-ger I4 lies below and in front of this common axis. The arrangement of the pivots which constitute the lower knuckle joints thus corresponds with the anatomical arrangement of the hand in nature, thusl enabling the ngers l|,. I2, I3 to be made of the same length, the fourth iinger i4 being somewhat shorter.

The opening and closing movements are communicated to the lingers and thumb by a screw and nut mechanism shown in Figs. 1 and 2 and in detailin Fig. 15. The screw 33 turns in a nut 34 fixed tothe base plate l5 and to an end ring 35 by a screw 36. The end ring 35 is arranged to fit on to the wrist plate of an artificial arm as described in U. S. application Serial No. 646,133

and rotary movement is communicated to the screw 33 by a driver 37 which receives a rotary movement from the fiexion cord through the elbow mechanism of the arm likewise as described in U. S. application Serial No. 646,133. The

driver 31 has a squared end fitting into a square hole in the screw 33, so that the screw 33 can move up and down relativelyto the driver 31 as it turns in the nut 34.

sitionon the trunnion block 4i bye platense@ The driver 3'! ispre- I vented from falling out of the screw by a washer VY38and pin 39.

.the arm50'. As therefore the screw-33 .more *op 'afweer screws-Tae, 'the .plate 4.1 .Shaving a thumb and a forked extension itorfeomi municating pivotal movement Lto the rngers.

As shown in Figs. :9 .and lv11o, "the membranenstirmtee 'by a skneton structure f-comuturea'iby e, light meta-l channel "53, the flanges foi fare joined byy a tube 5-2 mounted on andi-recite onthebea'ring-rod 25. Tne-n'anges ofthe annex are 7also joined by a pin 454 'engaging 'slotoirianddown, the saddle .pirce43l 'will risefan' all communicating pivotal movement fto' Tltl'x'e yth Y through the 'agency-of the arm'lSlland fil/iii' 'The thumb is enclosed by a 4preterm structure '56, carrying `a lcellulose acetate nail'i ane rubber gripping pad es. wnichrs sneed-over the metalgskel-eton and bonded-theretobiyfadhesiye or liquid plastic material. 'The ffork'e'd rearward extension 4 5 lv of the saddle piece 43de" pivote pin 59 'to the lower end of -alever-lill upper end of. which is pivoted bya ,.pi'n fork 62 (Fig. l1) pivoted centrally byfai 5' to '-a. V-shaped 'lever 63 (see. also Fig. f2). This leverv 63 has lat 'its ends forked portionsflwlfiih embrace the tie rods LIGand `so"corn'nethemoi/e ments of the llever "63 'to an up 'and 'dow'n'movementv or a rocking movement about'fthe'ipiv pin 65. At each end the lever '63 isfprovide `t'liia forwardly extending pin 65 on "which ''sfcetitrally pivoted a lever 6l. To the opposite. .ends f"`th'e levers'sr'are pivotedtliriks Safor impartiiigrgpvotal movement to the nngers, eachlink 68 'b'engfforked at its .lower end, see Figs. 6 an'dfl'to. 'embraoetlie associated end of lever '61 to which it i'siattaohd bye pin rs1..

AAs'shown in Figs. 6'7 13 and IILIthe-"Toitieripar't of eac'hin'ger comprises a. lightimetall'boforme di twoiiiembers (i9, 'l0 which are s'iiltlyfrltfed together and support between 'them fa .tube 'Tl mounted' itotur'n on the associatedbearingTod., i.' 'c fZG in the case of the 'first nge'r "H2, a tubular bearing -12 for permitting the-'upper ofthe ringer to turn relatively 'to'ithelovter' rt.. The upper part of each rlnger comprises* dfmetal strips 'i3 lunited by a 'pinfMito-ai T5 'mounted Ato turn in vthe 'bearing fetsef'alsio Fig. 3). The'upper end of each linktispivoteil byla `pin I6 to the. lower end of alinkIJI-a'ndialso to 'ai'steadyng lilik/T8 rotatablymollnddnfthe. tube 1l. The upper end of Athe llink"l1".pass'es through a slot lt in 'the bearing "T2 iirtofa.. slot 8(1 in the barrel l5, being securedto "thefbarrel byapinfsr. y

Asfthelinka moveslupand down thero'xiethe nn'geriscaused to open and closapivoti-ngboth about the vaxis of barrel'lE-which the Ymiddle'knuckle joint-and ab'outthef ttom ,''III'e loll/'elf palt vof "each 'finger fis" "ll metal gauze '82 (Fig. '7) and subsequently covered with plastic material, as linthe case loi'th'ebase.' The 1upp'erp'art of each ringer iis reiioase'dfby :la preformed plastic sheath 83, 'carrying f'a "7 and "rubber `pad 85, which 'correspondsfeiiactly"to that employed `furthe 'thumb and 'is Seciiredtofthe metars'tructure in similar fashion. 'Thelouler-end ofeach .plastic uppers'hea'threstsagains biittiiney tlsl 'of piasticimaterial attached to ftnevnuterfeirds oi thebal'rel 15h51 atpin. 81 '(Eig).

saddle piece 43. and levers KS3-,j lilfeoiietitiite fas aicompensating linkageiby"which .collective opening and closing movement is communicated to the ngers and thumb .from the screw-33., butwhich permits of continued movement after -any aon'e for more digits have been arrestedfof any vdigitsvvhic'zh have not beenarrested. The.actionzoftheflirikage insofar ras differential movement fof the rlngers'i's concerned, willfbe clear-from Figs. I'6-19.

v.ln Fig. llthe :parts are shown in the position they occupy with the ngers fully open. -In fFig. 17,1the 'rst two fingers have been larrestedlin va partly `closed position, and the third and fourth have moved on, the lever y63 having turnediaibout its'central pivot B5. v'In 18 the rst twofilngers have been arrested 'in the fully vopen 'positiom and there `has lbeen differential movement as between the third and 'tourthfmgers the left hand lever 611 having rocked about'its central "pivottopere mitthis. In Fig. 19, both levers v 6l 'have rocked about their central pivots.

Differential movement as vbetween Athe yf'ilngers and-thumbis permitted by virtue of pivotal movementor the-saddle piece -43 `on the trunnion's @5. Thus', the iin-gers lare-arrested, the saddle piece can y'turn about the rear pin v59, "as the trunni'on block moves up and d0wn,'to effect pivotal movement 'of ythe thumb. Similarly, if the thulbis arrested, the saddle vpiece -can turn 'about the forward ypin "54 to move the lingers.

"It will -be understood that the screw '33x1e'e`cl not derive rotary movement from `the felbow' mechanism described in U. S. application Serial No. 646,133. This could, if desired, be provided byattach-ment oi a Adisc to the outerend ofthe screw 'which could be turned by the wearerby' moving it Vagainst'the surface of a't'ableor'oth'er convenient object, lor rotated by the othe'rhand.

What I claim as my invention and idesire 5to secure by'Letters Patent is:

l. An vartificial hand, comprising a'base member, fa plurality of digits, consistingof'four'fingeifs and a thumb, all pivotally mounted lon "the L'base memberfor opening and closing movement inre. lation thereto, a screw and nut mechanism, one member 'of which is xed to the base member'and the other of which is adapted to receive rotary driving movement, a trunnion block rotatably mounted'on said other member, v'and a compeneating linkage connectingsaid other member'alnd the digits, andserving to 'impart collective pivotal movement to said digits on axial movement ."of said other member, said compensating linkage. comprising a saddle piece pivotally mounted "on the trunnionblock and having a forward vextensionpivotedtothe thumb, a main' lever pivoted intermediately to a rearward extension ofthe saddle piece, an end lever pivoted interrneiatjely` to each end of saidmain'lever andiingereoperating links pivoted at their opposite ends to -the fingers and to the ends of said end levers.

2. `artificial hand, comprising av base memberincluding a'skeleton metal structure and fa the `vdigits anda compensating linkage'connecting the-operating member and the digits andifs'erving to impart `collective movement `to the. ldigits 'from "the -operating lmember, said "linkage ipermittirig, lfzajtter aanyfof the digits has 4been -arrested,

continued movement fof "any lother fotftliei'diglts on continued movement of the operating member.

w 3.V An artiiicial hand, comprising a base memv ber including a skeleton metal structure, a stiffening wrapping of wire gauze surrounding said metal structure and an outer layer of plastic material applied to said wire gauze, a plurality of digits pivotally mounted on the base member for opening and closing movement in relation thereto, a common operating member for the digits which operates positively on them to open and close them and is self-locking against reverse operation by the digits and a compensating linkage connecting the operating member and the digits and serving to impart collective movement to the digits from the operating member, said linkage permitting, after any of the digits has been arrested, continued movement of any other of the digits on continued movement of the operating member.

4. An artiiicial hand, comprising a base member, a plurality of digits pivotally mounted on the base member for opening and closing move-- ment in relation thereto, each digit comprisinga hollow lower section pivoted at its lower end to the base member and constituted by a metal frame, a layer of wire gauze surrounding said frame, and an outer layer of plastic material applied to said wire gauze, and a hollow upper section pivoted to said lower section and comprising a metal frame and a preformed plastic sheath encasing said frame, a common operating member for the digits which operates positively on them to open and close them and is self-locking against reverse operation by the digits and a compensating linkage connecting the operating member and the digits and serving to impart collective movement to the digits from the operating member, said linkage permitting, after any of the digits has been arrested, continued movement of any other of the digits on continued movement of the operating member.

5. An artificial hand, comprising a base member, four fingers pivotally mounted on the base member for opening and closing movement in relation thereto, and an axially movable operating member for the fingers which operates positively on them to open and close them and is selilocking against reverse operation by the digits, and a compensating linkage connecting said operating member and said fingers, said compensating linkage comprising a main lever mounted centrally for pivotal movement in relation to the operating member, said main lever having forked endswhich engage and are slidable in relation to fixed parts f the base member, an end lever pivoted intermediately to each end of said main leverA and nger-operating links pivoted at their opposite ends to the iingers and to the ends of said end levers.

6. An artiiicial hand comprising a base mem-- ber, a plurality of digits consisting of four fingers anda thumb all pivotally mounted on said base member for opening and closing movement inrelation thereto, a screw and nut mechanism on said base member, means operable by the wearer of the hand for causing relative rotation between the members'of said screw and nut mechanism and thereby for causing' one of the saine to reci rocate relative to the other, a lever extending across said reciprocating member and pivotally mounted intermediate its ends thereon to be 'rockable about an axis transverse to the axis of said reciprocating member, means pivotally connected to one end of said lever for rocking said 8, thumb digit to Open and close the same as said reciprocating member reciprocates, and means connecting the "opposite end `of said lever With said four fingerA digits for imparting opening and closing movement thereto as said reciprocating member reciprocates.

7. An artificial hand comprising a base member, a plurality of digits consisting of four lingers and a thumb all pivotally mounted on said base member for opening and closing movement in relation thereto, an operating member mounted on said base member for reciprocation relative thereto, means operable by the wearer of the hand for reciprocating said operating member positively forward and back, a lever extending across said operating member and pivotally mounted intermediate its ends thereon to be rockable about an axis transverse to the axis of said member, means providing a pivotal connection between one end of said lever and said thumb digit for rocking said digit to open and close the same as said operating member reciprocates, and lever and linkage connection means between the opposite end of said lever and said four nger digits for opening and closing said'nger digits upon reciprocating movement of said operating member and for continuing the closing movement of those nger digits which are free from closing obstructions, upon continued movement 0f said operating vmember in digit closing direction, while permittingthe otheriinger digits to be arrested against further closing movement when reaching an obstruction.

8. An articial hand comprising a base member, a plurality of digits consisting of four ngers and a thumb all pivotally mounted on said base member for opening and closing movement in relation thereto, an operating member mounted on said base member for reciprocation relative thereto, means operable by the wearer of the hand for reciprocating said operating member positively forward and back, a lever extending across said operating member and pivotally mounted intermediate its ends thereon to be rockable about an axis transverse to the axis of the said member, means for rocking said thumb digit to open and close the same as said op-erating member reciprocates including a pivotal connection between one end of said lever and Said thumb digit -about which said lever will rock whenever closing movement of said digit is arrested by said digit striking an obstruction, and connections between the opposite end of said lever and said four finger digits for imparting opening and closing movement to the latter as said operating member reciprocates, said connections including a link, a pivotal connection between said link and the opposite end of said lever about which said lever will rock whenevei` closing movement of any of said nger digits is arrested by said digit striking an obstruction, a second lever, connections between said link and said second lever for imparting movements oftranslation to said second lever as said link reciprocates with said operating member, said connections including a pivot intermediate said second lever about which the same can oscillate, and connections from opposite ends of said second lever and said finger digits including levers and links arranged to cause continued closing movement of all unobstructed ones of said ringer digits upon continued movement of said operating member, after any of said digits has been arrested by striking an obstruction.

9. An artificial hand, comprising a base member, a plurality 'of digits consisting of four fingers and a thumb all pivotally mounted on said base member for opening and closing movement in relation thereto, an operating member mounted on said base member for reciprocation relative thereto, means operable by the wearer of the hand for reciprocating said operating member positively forward and back and for self-locking said operating member in operated position, a main lever extending across said operating member and pivotally mounted intermediate its ends for rockable movement about an axis transverse to the direction of reciprocation of said operating member, means connecting the pivot mounting of said main lever to said operating member for reciprocating movement with said operating member; lever and linkage connection means between said main lever and all of said iinger digits for open-- ing and closing said digits upon reciprocating movement of said operating member and for continuing the closing movement of those finger digits which are free from closing obstructions, upon continued movement of said operating member in digit closing direction, while permitting the other finger digits to be arrested against further closing movement when reaching an obstruction, and a linkage between said operating member and said thumb digit separate from said main lever, for positively opening and closing said thumb digit upon reciprocating movement of said operating member, said linkage comprising a lost motion connection permitting the continued closing movement of the unobstructed finger digits, upon obstruction of said thumb digit against further closing movement.

10. An artificial hand comprising a frame structure including a pair of substantially parallel tie rods extending lengthwise of the hand, a plurality of digits mounted on said structure for opening and closing movement in relation thereto, an operating member mounted on said structure for bodily rectilinear movement lengthwise of said hand, means for bodily moving said operating member under control of the wearer, a main lever pivotally mounted on said operating member intermediate its ends for bodily moving said main lever with said operating member along said hand and for pivotally moving said main lever with respect to said oper-ating member about the pivotal axis, said axis being transverse to the length of said lever, said main lever having means guiding its ends along said tie rods during movements thereof, end levers each pivoted intermediately of its ends respectively to an end of said main lever, and a digit operating linkage mechanism between each end of each of said end levers and a corresponding digit for imparting opening and closing movement to said digits as said operating member moves and for causing continued closing movement of all unobstructed digits upon continued closing movement of said operating member in digit closing direction, after any of said digits has been arrested by striking an obstruction.

EDWARD WALTER HOBBS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 51,238 Snellerberg Nov. 28, 1865 670,684 Mueller Mar. 26, 1901 2,028,670 Hosking Jan. 21, 1936 2,230,378 Eberle Feb. 4, 1941 2,301,009 Becker Nov. 3, 1942 2,364,313 Pecorella Dec. 5, 1944 FOREIGN PATENTS Number Country Date 132,859 Great Britain Sept. 23, 1919 315,842 Germany Nov. 14, 1919 558,963 France June 6, 1923 

